Gaskets are used to provide a seal between two engaging surfaces. For example gaskets are used in window assemblies to provide a seal against external air infiltration and water leakage. In a typical window assembly, in order to provide a tight seal, the gasket material must be somewhat resilient and able to conform to any irregularities between the mating surfaces of the window glass and a structural component such as a window frame. In applications where an engaging surface such as the glass slides across a face of a gasket generating lateral forces, the gasket must also provide resistance to tearing. Examples of applications where the gasket must resist tearing due to sliding or lateral movement of an engaging surface include sliding glass doors and automotive sunroofs. Typically, gaskets are prepared from elastomeric materials including natural or organic and synthetic rubbers, such as EPDM, SBR, butyl, nitrile and neoprene, chlorosulfonated polyethylene, fluorocarbon containing compounds, urethanes and silicones. Silicone rubbers have excellent molding and extrusion properties and are used to form gaskets with good temperature resistance, resistance to compression set and tensile strength. In stationary sealing applications, silicone rubber gaskets perform well. However, silicone rubber inherently possesses a high coefficient of friction and thus in applications where one or both mating surfaces in contact with the gasket may move lateral to the surface of the gasket there is a tendency to tear. Silicone rubber formulations having good resistance to tear generally are not pliant enough to provide an effective seal in relatively low pressure applications such as automotive sunroofs. Therefore, in applications where lateral forces are generated on the gasket, silicones have not been the material of choice.
U.S. Pat. No. 4,223,897 discloses an anti-stick, non-liquid absorbing laminated gasket The laminated gasket comprises a metallic core and a bonded fibrous layer. The fibrous layer contains a liquid impermeable, resinous impregnate. An anti-stick coat lies along an outer face of the fibrous layer. The anti-stick coat is selected from a group consisting of polytetrafluoroethylene, silicones, polysiloxanes talc, and bentonite. The gaskets are used to seal stationary mating surfaces against fluid leaks in conduits for steam or air, and automotive parts such as carburetors, manifolds and cylinder heads.
U.S. Pat. No. 5,368,315 discloses a non-stick automotive gasket which comprises a resilient material having a polymeric fluorocarbon coating obtained by impregnating the resilient material with a saturant having dispersed therein polymeric fluorocarbon particles. The non-stick gaskets of the patent are used to seal stationary mating surfaces.
U.S. Pat. No. 5,468,815 discloses a curable silicone release formulation for preparing a laminate of a substrate and adhesive. In this application the user typically applies one face of the adhesive to a surface with a release liner in place on the second exposed adhesive surface. The applicator then applies pressure to the release liner to secure the adhesive to the surface. In applying pressure to the release liner, a user often encounters resistance due to friction. The cured coating of the patent is said to reduce the coefficient of friction in this instance.
U.S. Pat. No. 5,080,973 discloses a low friction, high adhesion release coating for disposable diaper tape based on at least 15% by weight of a reactive polydialkylsiloxane, preferably a reactive dimethylsiloxane, at least 40% by weight of a reactive silicone high adhesion agent and crosslinking agent. The composition contains a suitable noble metal catalyst and is heat cured.
None of the above patents disclose a method of lowering the coefficient of friction of a gasket by coating the gasket with a composition containing a curable silicone resin and a lubricating filler which is not soluble in the coating properties.